The present invention relates to a link information management method for use with an apparatus or a system (e.g. geographical information system) which handles area information (geographical information, document, drawings, etc.) and attribute information (information stored in database or file, etc.).
Geographical information systems have hitherto been known as a system for supporting data retrieval/reference by using a corresponding relationship between geographical information and attribute information. The geographical information system has a fundamental function to retrieve attribute information such as geographical information and residents information from each other. For example, the geographical information system is able to display residents information by designating a house on a map. Conversely, the geographical information system is able to display a house of a corresponding resident on a map by designating a name of the resident in the residents information. As the geographical system having the above-mentioned functions, there has hitherto been known a self-governing body geographical system "ARISTOWN" (PIXEL, No. 56, pp. 73-78) having a function to make use of maps and attribute information such as road information and land information in association with each other.
To realize the fundamental function of the geographical information system, a correspondence relationship (hereinafter referred to as "link information") between geographical information and attribute information should be saved in some form. Therefore, when the operation of the geographical information system is started, a registration work for registering link information is indispensable for the operation of the geographical information system. Further, while the geographical information system is operated, maintenance for each of geographical information, attribute information and link information becomes necessary. In a link information registration processing or a link information maintenance processing, since link information is registered and changed while a corresponding relationship between geographical information and attribute information is constantly maintained, the link information registration processing and the link information maintenance processing become cumbersome as compared with the case where geographical information and attribute information are each registered and changed. Moreover, as the scale and the kind of geographical information and attribute information to be handled increase, the record number of registered link information increases in a combinatorial mathematics fashion. For the above-mentioned reason, there are required many steps of link information registration and maintenance work. To solve this problem, there has been considered a support technology in order to decrease the number of steps of the link information registration and maintenance work.
For example, as a support technology for supporting a link information registration, U.S. Pat. No. 5,625,771 describes a character cursor function. According to the character cursor function, when geographical information and attribute information are associated with each other, an amount of an operator eye movement with respect to a display screen can be decreased and an efficiency of a link information registration processing can be increased by displaying a part of attribute information near a mouse cursor.
Also, as a technology for supporting a link information maintenance, there is a technology (JP-A-7-73297) for automatically maintaining names of residents on maps by using link information between residents information and geographical information. According to this technology, when a resident of a certain house is changed from the state that geographical information and residents information with respect to the above-mentioned house are linked, for example, a written name of a resident contained in geographical information to which changed resident information should be linked can be changed automatically.
Further, as another technology for supporting a link information maintenance, there has hitherto been known a technology (JP-A-6-28438) for executing a link maintenance between an old map and a new map by correcting position information of link information corresponding to a closed area on the old map. According to the above-mentioned technology, when link information of the old map and the new map in which position information is slightly changed with respect to the old map is corrected (e.g. a map of 1996 edition is changed to a map of 1997 edition), position information which was included in link information of the old map is corrected and then copied to the new map.
As described above, when the geographical information system is operated, there is examined a technology for supporting an access and maintenance of link information.
On the other hand, the above-mentioned conventional technologies are not satisfactory in supporting the access and maintenance of link information. For example, the above-mentioned character cursor function is unable to support the case where there exists link information that has already been registered. That is, when geographical information is updated under the situation that link information has been already registered on geographical information, the character cursor function is able to only display attribute information obtained before the link information is registered near a cursor. Therefore, link information with respect to current geographical information has to be re-registered one more time from the beginning. That is, the link information that has already been registered cannot be used effectively.
JP-A-7-73297 describes a technology for updating geographical information and residents information when there already existed link information. However, this technology has no support function to support the case where residents information is registered additionally after the link information has been registered. Considering this technology from a system operation standpoint, when new residents information is additionally registered after link information has been registered, it is frequently observed that there occurs residents information which is not corresponding to geographical information (i.e. there exists no link information). However, according to the method described in JP-A-7-73297, the residents information that is additionally registered after the link information has been registered is missed, and hence the residents information that was additionally registered cannot be supported by the link maintenance processing.
Also, JP-A-6-29438 is unable to maintain link information when a scale or a direction is different between old and current geographical information. On the other hand, considering this technology from a system operation standpoint, a class of geographical information that is made corresponding to attribute information also should be changed as business contents handled by the geographical information system are changed. Also, since a business becomes complicated, detailed geographical information become necessary so that a map of scale, 1-50,000 should be changed to a map of scale, 25,000. However, according to the method described in JP-A-6-28438, link information is maintained in a manner in which position information of link information registered on the old map is succeeded substantially as it is. Therefore, when scales or directions of old geographical information and current geographical information are considerably different from each other, link information registered on the old geographical information cannot be correctly changed to link information of current geographical information.
Incidentally, JP-A-9-282330 describes a system for supporting a construction of a database by associating the database and documents as a system similar to the geographical information system. Also in the system described in JP-A-9-282330, link information by which the database and documents are associated with each other should be registered and maintained similarly to the geographical information system. As a result, there arises a problem similar to the above-mentioned problem from a standpoint of the number of steps in the link information registration and maintenance processing similarly to the geographical information system.